Telephone system.



PATENTED AUG. 25, 1908;

H. G. WEBSTER.

TELEPHONE SYSTEM.

APPLIOATION FILED MAR. 5, 1906.

s a H lll l l l lr*lll l lllHlw ca, WASHINGTON. n. c.

UNITED sTATEs PATENT OFFICE.

HARRY G. WEBSTER, OF CHICAGO, ILLINOIS, ASSIGNOR TO MILO G. KELLOGG, OFCHICAGO,

- ILLINOIS.

TE LE PHONE SYSTEM.

No. 897,241. I

Specification of Letters Patent.

Patented Aug. 25, 1908.

Application filed. March 5, 1906. Serial No. 304,229.

' telephone lines extending to the central office are inductively,rather than conductively, united for conversation. In such systems,

the telephone lines form conductively independent circuits, and anintermediate circuit connects these telephone line circuits forconversation through the agency of repeating coils.

One feature of my invention consists in including the supervisory lampsdirectly in bridge of this intermediate circuit. I have found that sucha bridge, although substantially devoid of impedance, will not materially interfere with speech transmission over the circuit, provided thelatter is substantially free from resistance and impedance. By providingthe windings of the repeating coils, which are included in thisintermediate circuit, with relatively few turns, it is possible toaccomplish this result. With this ar rangement, the potential induced inthis intermediate circuit is relatively low, and consequently thepossibility of cross talk is greatly reduced.

Another feature of my invention consists in a novel arrangement ofcircuits and apparatus, capable of use with such an intermediate talkingcircuit, for the control of the line and supervisory signals.

These and other features and objects of the invention will more fullyappear upon reference to the following detailed description taken inconnection with the accompanying drawing, and the scope of the inventionwill be particularly indicated in the appended claims.

In the drawing, which illustrates diagrammatically a telephone systemembodying the features of the present invention, A and B designatesubstations which are connected to a central office C by suitabletelephone lines. The equipment at substation A, which may be of anypreferred type, is here shown as comprising a call-bell 1 in series witha condenser 2, included in a normally closed bridge ductor' 14.

I of the telephone line limbs 34 by the engagement of the switch-hook 5with the con tact 6. A second bridge, normally open and including thetransmitter 7 and a winding of the induction coil 8, is closed at thecontact 9 by the switch-hook 5 whenever the receiver 10, which isincluded in a local circuit with the other winding of the induction coil8, is removed therefrom. At the central oflice, the circuit of the linelimbs is completed through the winding 11 of the repeating coil R andthe batteries 12 and 13. One section of the winding 11 connects the linelimb 3 with the grounded side of the battery 13, while the other sectionconnects the line limb 4with the live pole of the battery 12 byaconductor 14, the batteries being thus connected in series between thesections of the winding.

The other winding 15 of the repeating coil R, also shown in twosections, is permanently included in a branch extending from the linejacks 16 to the armature contact 17 of the line relay 18. This branch isnormally completed to the live pole of the battery 12 by way of the linerelay contact 19 and the con- Upon the attraction of the armaturecontact 17 into engagement with the contact 20, this branch is completedby way of the conductor .21. to the live pole of the battery 13. Fromthis, it will be seen that current of different potentials will besupplied to the jacks 16 in accordance with the operative condition ofthe line relay contacts. The line relay 18 is provided with a secondarmature contact 22 which is adapted, upon the energization ofthe'relay, to engage a fixed contact 23, normally to complete a circuitfrom the live pole of the battery 12 through the line lamp 24 to ground,by way of the normally closed contacts 25 and 26 of the cut-off relay27. The line relay 18 has its winding directly included in the line limb4 and is consequently provided with some means for rendering the relaynon-inductive so as to prevent interference with speech transmissionover the line. In the present instance, this is accomplished by means ofa non-inductive shunt 28. The cut-of]? relay 27 has its windingconnected in parallel with the winding 15 of the repeating coil R.

The equipment and the connections thus far described with reference tosubstation A are duplicated in connection with substation B, and thecorresponding parts are there indicated by similar primed characters.

sections 29 and 29.

Upon reference to the two stations, it will be seen from ,the matterthus far described that the apparatus at each station is included in aline circuit extending through the winding 11, or 11, of the repeatingcoil R, or R, and the batteries 12 and 13, and that these line circuitsare adapted to be inductively united by an intermediate circuit which isadapted to be completed between the jacks 1616 by a link-circuitcomprising a single strand made up of the sections 2929, uniting theanswering and calling plugs 30 and 30respectively. The supervisorylamps31 and 31, which are preferably the usual incandescent electric lamps,are connected respectively between ground and the strand These sectionsare separated by the usual condenser 32 which will permit the passage ofvoice currents, but will prevent the passage of battery current. Theusual listening-key 33 is provided. This key controls a branch leadingfrom the strand section 29 to ground through a condenser 34, theoperators receiver 35 and the secondary winding of an induction coil 38.The primary winding of the induction coil is included in a local circuitin series with the operators transmitter 37, and the battery 38. Thetertiary winding of the induction coil 36 is connected between a testingtip contact on the calling plug 30 and the live pole of the battery 12.The strand 29 is also provided with a ringing-key 39 which normallyengages the contact 40 to maintain the continuity of the strand, but isadapted to be depressed into engagement with the contact 41- to connectthe live pole of the ringing generator 42 to the calling plug 30.

In the operation of the system, a party at substation A, desiring toconverse with a party at substation B, removes his receiver from itshook and thereby completes the line circuit through the winding of theline relay 18, winding 11 of the repeating coil R and the batteries 12and 13 in series. pletion of this circuit energizes the relay 18sufliciently to attract its armature contacts 17 and 22by the formerconnecting the low potential battery 13 in circuit with the jacks 16,and by the latter completing the circuit of the line lamp 24 from thelive pole of the battery 12 to ground, thereby causing the illuminationof said lamp, as an indication to the operator that connection isdesired. Upon observing this signal, the operator will insert theanswering plug 30 into a jack 16 and thereby complete a circuit fromground, through the supervisory lamp 31, strand section 29, plug 30, ack16, through the winding 15 of the repeating coil R and the winding ofthe cutoi'l relay 27 in parallel, through the line relay contacts 1720,conductor 21 and battery 13 to ground. The flow of current over thiscircuit, by reason of the low potential of the battery 13, is insuf- Thecom-,

ficient to cause the illumination of the lamp 31, but is sufficient tocause the separation of the cut-off relay contacts 2526 to extinguishthe line lamp 24. Upon the insertion of the plug 30 into the jack 16,the operator will depress her listening-key 33 and thereby complete atalking circuit from ground at the induction coil 36, through thesecondary winding of said coil, the operators receiver 35, condenser 34,listening-key 33, condenser 32, strand 29, plug 30, jack 16, repeatingcoil winding 15, line relay contacts 1720, conductor 21 and battery 13to ground. Over this circuit and the line circuit in inductive relationthereto, she may converse with the party at substation A to learn hiswishes. Upon learning that connection is desired with telephone line3'4, she will touch the tip of the calling plug 30 to the testingcontact of one of the jacks 16 to determine the idle or busy conditionof the line, while main-' taining the listening key 33 depressed. Fromthe circuits previously traced, it will be seen that if the line 34 isbusy, a potential will exist at the contact touched, due to theconnection over some other link-circuit with the live pole of thebattery 13. Since the testing contact of the plug 30 is directlyconnected to the live pole of the battery 12, there will be a differencein potential between said contact and the testing contact of the jack.Consequently, there will be a current flow through the tertiary windingof the induction coil 36, which will cause a click in the operatorsreceiver 35, as an indication to her that the line is busy. If the lineis idle, the potential of the testing contact of the jack will be thatdue to the connection with the live pole of the battery 12. Thisconnection extends from the live pole of the battery, through the linerelay contacts 19-17, the winding 15 of the repeating coil R, to thejack. Consequently, upon touching the testing contact of the plug 30thereto, there willbe no flow of cur rent and no resultant click. If itis found, upon making this test, that the line 3-4 is idle, the operatorwill insert the calling plug 30 into the jack 16 and depress herringing-key 39 to operate the call-bell 1 at the substation B. At thispoint, it may be noted that when the calling plug 30 is inserted intothe jack 16, the testing tip contact of the plug passes beyond, and outof engagement with, the spring contact of the jack. The depression ofthe ringing-key will complete a circuit from the live pole of thegenerator 42, through the listening-key contacts 4139, calling plug 30,jack 16, repeating coil'winding 15 and the winding of the cut-off relay27"in parallel, the line relay contacts 1719, conductor 14 and batteries12 and 13 to ground. The alternating current in this circuit will inducea current over the line limbs 3-4 and "answering of the call at .thesubstation and after the plug 30 has been inserted into the jack 16, thesupervisory lamp 31 will be illuminated by reason of a circuit fromground, through said lamp, strand 29, plug 30, jack 16, repeating coilwinding 15 and the winding of the cut-off relay 27 in paral- 101, linerelay contacts 1719, conductor 14, batteries 12 and 13 to ground. By

reason of this connection to the batteries 12- and 13,the currentthrough the lamp 31 is sufficient to cause its illumination, and itwillremain in this condition until the receiver 10 at the substation B isremoved from its hook. The flow of current from this high potentialsource is also sufl icient to separate the cut-off relay contacts 25 and26, thereby removing the control of the line lamp 24 from substation B.Upon the removal of the receiver 10 at the substation B, the cur rentflow over the line circuit will energize the line relay 18 sufficientlyto attract its armature 17 to interrupt the connection of thesupervisory lamp 31 to the live pole of the battery 12, whichconstitutes a high potential source, and to replace it by a connec tionto the live pole of the battery 13 which constitutes a low potentialsource. As previously indicated, the resulting current flow will beinsufficient to maintain the supervisory lamp 31 illuminated, but willbe sufficient to maintain the cut-off relay contacts out of engagementand therefore to maintain the line lamp extinguished.

From the above description, it will be seen that the line circuits,which include the windings 11, or 11, of the repeating coils, areconductively independent of each other and of the intermediate circuitby which they are connected for conversation. The latter circuitprovides a path between the terminals of the windings 15 on the one handand 15 on the other. As indicated in the diagram, the connection betweenthe upper terminals of these windings includes the jacks 1616 and theconnecting link-circuit, while the connection between the lowerterminals of the same windings will include either the conductors 14 and14 or 21 and 21, according to the position of the line relay armaturecontacts 1717. In the former case, the batteries 12 and 13 are connectedin series bridge of this circuit; and in the latter case, the battery 13alone is connected in bridge. At all times, the supervisory lamps 31 and31 are included in bridge of this circuit and that of the windings 15and 15 of the repeating coils, and obviously these may be made of verylow resistance. The bridges including the supervisory lamps 31 and 31,as previously pointed out, do not interfere with speech transmissionover this intermediate circuit, under the circuit conditions indicated.

In carrying out my invention, obviously many modifications may be madetherein without departing from the spirit and scopeof my invention. I,therefore, do not wish to be limited to the specific matter illustrated, but aim to cover, by the terms of the appended claims, all suchmodifications. In these claims, I have used the term, cut-off relay, inits broad sense to cover any relay by which the substation control ofthe line signal is destroyed.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is 1. A telephone system comprising a plurality of telephonelines extending from substations to a central office, means at thecentral office for inductively uniting said lines for conversation by atalking circuit substantially devoid of resistance and impedance,

and an electrically actuated signal connected in bridge of said circuit,said bridge being substantially devoid of impedance.

2. A telephone system comprising a plurality of telephone linesextending from substations to a central office, means at the centraloffice for inductively uniting said lines for conversation by a talkingcircuit substantially devoid of resistance and impedance, and anincandescent signal-lamp, and that only, connected in bridge of saidcircuit.

3. A telephone system comprising a plurality of telephone linesextending from sub stations to a central office, means at the centraloffice for inductively uniting said lines for conversation by a talkingcircuit substantially devoid of resistance and impedance, and a signaloffering n.oninductive resistance, and that only, in bridge of saidcircuit.

4. A telephone system comprising-a plurality of telephone linesextending from substations to a central office, repeating coils and anintermediate connecting circuit for uniting said. lines forconversation, said. circuit being substantially devoid of resistance andimpedance, and an electrically actuated signal connected in bridge ofsaid circuit, said bridge being substantially devoid of impedance.

5. A telephone system comprising a plurality of telephone linesextending from substations to a central office, repeating coils and anintermediate connecting circuit for unit ing said lines forconversation, said circuit being substantially devoid of resistance andimpedance, and a signal offering non-inductive resistance, and thatonly, in bridge of said circuit.

6. A telephone system comprising a plurality of telephone linesextending from substations to a central office, a normally open circuitat the central office substantially devoid of resistance and impedance,means included therein for inductively unitingsaid lines forconversation when said circuit is completed, a single strandlink-circuit for completing said circuit, and an electrically actuatedsignal included in bridge between the link-circuit strand and the otherleg of said normally open circuit, said bridge being substantiallydevoid of impedance.

7. A telephone system comprising a pinrality of telephone linesextending from substations to a central office, a normally open circuitat the central office substantially devo1d of resistance and impedance,means 111- cluded therein for inductively uniting said lines forconversation when said circuit is completed, a single strandlink-circuit for completing said circuit, and a signal offeringnon-inductiveresistance, and that only, included in bridge between thelink-circuit strand and the other leg of said normally open circuit.

8. A telephone system comprising a plurality of telephone linesextending from substations to a central office, a normally open circuitat the central office substantially devoid of resistance and impedance,means included therein for inductively uniting said lines forconversation when said circuit is completed, a single strandlink-circuit for completing said circuit, and an incandescentsignal-lamp, and that only, connected in bridge between the link-circuitstrand and the other leg of said normally open circuit.

9. In a telephone system, the combination of a conductor extendingbetween two stations, an electrically actuated signal and sources ofcurrent of different potentials associated therewith, means under thecontrol of one station to supply current to said signal from said highpotential source to cause the display of said signal, and means underthe control of the other station for substituting said low potentialsource of current for said high potential source to cause the eifacementof said signal.

10. A telephone system comprising a telephone line extending from asubstation to a central station, a link-circuit for making con nectionto said line, means for holding conversation over said line andlinkcircuit, sources of current of different potentials, an electricallyactuated signal, means under the control of one station to supplycurrent to said signal from the high potential source, and means underthe control of the other station for substituting said low potentialsource of current for said high potential source to cause the effacementof said signal.

11. A telephone system comprising a tele phone lineextending from asubstation to a central station, a connection terminal for said line, arepeating coil for inductively uniting said line to said terminal, alink-circuit for making connection to said terminal to establish aconversational circuit, sources of current of different potentials, anelectrically actuated signal, means under the control of one station tosupply current to said signal from the high potential source, and meansunder the control of the other station for substituting said lowpotential source of current for said high potential source to cause theeffacement of said signal.

12. A telephone system comprising a telephone line extending from asubstation to a central station, a connection terminal for said line, arepeating coil for inductively uniting said line to said terminal, alink-circuit for making connection to said terminal to establish aconversational circuit, sources of current of different potentials, anelectrically actuated signal, means under the control of one station forsupplying current to said signal from the high potential source throughone of the repeating coil windings to cause the display of said signal,and means under the control of the other station for substituting saidlow potential source of current for said high potential source to causethe effacement of said signal.

13. A telephone system comprising a telephone line extending from asubstation to a central office, a link-circuit for making connection tosaid line, means for holding conversation oversaid line andlink-circuit, sources of current of different potentials, a signalassociated with said link-circuit, means operative upon the connectionof said link-circuit to said line to supply current to said signal fromthe high potential source to cause its display, and means under thecontrol of the subscriber for substituting said low potential source forsaid high potential source to cause the effacement ofsaid signal.

14. A telephone system comprising a telephone line extending from asubstation to a central office, a connection terminal for said line, arepeatin coil for inductively uniting said line to sai terminal, alink-circuit for making connection to said terminal to estab lish aconversational circuit, sources of current of different potentials, asignal asso ciated with said link-circuit, means operative upon theconnection of said link-circuit to said terminal to supply current tosaid signal from the high potential source to cause its display, andmeans under the control of the subscriber for substituting said lowpotential source for said high potential source to cause the effacementof said signal.

15. A telephone system comprising a telephone line extending from asubstation to a central office, a connection terminal for said line, arepeating coil for inductively uniting said line to said terminal, alink-circuit for making connection to said terminal to estabseam lish aconversational circuit, sources of current of different potentials, asignal associated With said link-circuit, means operative upon theconnection of said link-circuit to said terminal to supply current tosaid signal from said high potential source through one of the repeatingcoil windings to cause the display of said signal, and means under thecontrol of the subscriber for substituting said low potential source tocause the etlacement of said signal.

16. A telephone system comprising a telephone line extending from asubstation to a central station, a link-circuit for making connection tosaid line, means for holding conversation over said line andlink-circuit, sources of current of different potentials, a line signalnormally under the control of the subscriber, a cut-oil relay fordestroying said control, a link-circuit signal, means normally operativeupon the connection of said linkcircuit to said line to supply currentfrom said high potential source to said link-circuit signal to cause itsdisplay and to said cut-oil relay to cause the attraction of itsarmature, and means under the control of the subscriber for substitutingsaid low potential source of current for said high potential source tocause the efl'aeement of said linkcircuit signal and to maintain saidcut-oil relay armature attracted.

17. A telephone system comprising a telephone line extending from asubstation to a central office, a connection terminal for said line, arepeating coil for inductively uniting said line to said terminal, alink-circuit for making connection to said terminal to establish aconversational circuit, sources of current of different potentials, aline signal normally under the control of the subscriber, a cut-offrelay for destroying said control, a link-circuit signal, means normallyoperative upon the connection of said link-circuit to said terminal tosupply current from said high potential source to said link-circuitsignal to cause its display and to said cut-ofl' relay to cause theattraction of its armature, and means under the control of the subscriber for substituting said low potential source of current for saidhigh potential source to cause the eflacement of said linkcircuit signaland to maintain said cut-oil relay armature attracted.

18. A telephone system comprising a telephone line extending from asubstation to a central office, a link-circuit for making con-= nectionto said line, means for holding conversation over said line andlink-circuit, sources of current of different potentials, a line signal,a line relay for controlling the display of said signal, a cut-off relayfor de' stroying said control, a link-circuit signal, means normallyoperative upon the connection of said link-circuit to said line tosupply current from said high potential source to said link-circuitsignal to cause its display and to said cut-oii relay to cause itsactuation, and means under the control of the subscriber operativenormally to energize said line relay to display said line signal andoperative after the connection of said link-circuit to said line tosubstitute said low potential source of current for said high potentialsource in the link-circuit signal and cut-oil relay circuit to cause theeflaccment of said link-circuit signal and to maintain said cut oilrelay actuated.

19. A telephone system comprising a telephone line extending from asubstation to a central oihce, a connection terminal for said line, arepeating coil for inductively uniting said line to said terminal, alink-circuit for making connection to said terminal to establish aconversational circuit, sources of current of different potentials, aline signal, a line relay for controlling the display of said signal, acut-off relay for destroying said control, a link-circuit signal, meansnormally operative upon the connection of said link-circuit to saidterminal to supply current from said high potential source to saidlink-circuit signal to cause its display and to said cut-oil relay tocause its actuation, and means under the control of the subscriberoperative normally to energize said line relay to display said linesignal and operative after the connection of said link-circuit to saidterminal to substitute said low potential source of current for saidhigh potential source in the link-circuit signal and cut-off relaycircuit to cause the eilacement of said link-circuit signal and tomaintain said cut-oil relay actuated.

In Witness whereof, I hereunto subscribe my name this 3rd day of March,1906.

HARRY G. WEBSTER.

Witnesses:

A. H. DYsoN, GEO. E. MUELLER.

